How often do elite 40-yard dash times translate to successful NFL careers?

Before they can realize their dream of being drafted, more than 300 prospects will participate in the NFL scouting combine this week in Indianapolis. Scouts combine each player's combine performance with tape from his college career to get a complete picture of how his athleticism projects to the professional level.

In theory, the numbers that come out of this week's workouts would help determine whether or not a player has the physical tools and potential to excel in the pros. But it’s worth wondering whether strong combine performances actually correlate with successful careers. This question comes up often with the 40-yard dash, which has become the marquee event of the combine each year as players work to shave hundredths of a second off their times and climb up draft boards.

An athlete may put up a record time in the 40-yard dash, but is that raw straight-line speed valuable for NFL teams?

Using combine data dating back to 1999, we set out to answer whether players with faster 40 times succeed in the NFL at a greater frequency.

Running backs

Chris Johnson, who holds the combine record with his 4.24 40-yard dash time, reached three Pro Bowls in his first three seasons with the Tennessee Titans after being drafted with the 24th pick of the first round in 2008. Of the top-flight speedsters, his career is one of the most prominent success stories.

Johnson put together six straight 1,000-yard rushing seasons and even eclipsed the storied 2,000-yard plateau by six yards back in 2009, a season that earned him his "CJ2K" moniker. But after signing a four-year contract extension worth over $50 million prior to the 2011 season, Johnson was never the same game-changing force he had been.

In 2013, he finished with a career-low 3.9 yards per carry. After being cut by the Titans, he spent the 2014 season with the Jets and failed to top 1,000 yards for the first time in his seven-year career. The Jets declined to pick up Johnson’s option for next season, and despite a tremendous start to his career, the 29-year-old appears to have lost the blazing speed that made him such an invaluable asset as a younger player.

The jury is still out on Kent State product Dri Archer, who posted the top 40-yard dash at last year's combine but only received 10 carries with the Pittsburgh Steelers as a rookie. If Archer never catches on, he would join a long list of sub-4.4 guys—Darren McFadden, Derrick Blaylock, LaMichael James, Cedric Peerman and Ben Tate, among others—who haven’t found consistent production in the NFL after dazzling in the college ranks with their speed.

Wide receivers

It's almost ominous how poorly a fast 40 time predicts success for young receivers. Guys like Trindon Holliday, Jacoby Ford, Darrius Heyward-Bey and Johnny Knox all posted 40 times under 4.3 seconds, but their pro careers were either short-lived or of negligible impact.

On the opposite end of the spectrum, a variety of receivers who ran 40s slower than 4.4 seconds went on to productive careers. From those who parlayed their consistency into long careers (Torry Holt, Laveranues Coles, Marques Colston, Deion Branch and Greg Jennings) to younger players who have showcased the talent to play faster than their raw numbers suggest (Randall Cobb, A.J. Green, Torrey Smith and Jeremy Maclin), the 4.4-to-4.5 range has produced several success stories since 1999.

Receivers no doubt need to possess a burst of acceleration, but treating speed as the most important factor in the evaluation process hasn't proved fruitful, most notably when Al Davis’ Raiders took Heyward-Bey with the No. 7 pick in 2009 over future Pro Bowlers Maclin, Percy Harvin and Mike Wallace.

A combination of precise route-running, ball skills, physical size and all-around football IQ have been far better indicators of future success for skill players in the past 16 drafts.

So exercise caution in March and April as prospects climb up draft boards on the strength of impressive 40-yard dash times at the combine. Just because a player would make a great track star doesn’t mean he’s destined to shine on Sundays.

More NFL

We've Got Apps Too

Get expert analysis, unrivaled access, and the award-winning storytelling only SI can provide - from Peter King, Tom Verducci, Lee Jenkins, Seth Davis, and more - delivered straight to you, along with up-to-the-minute news and live scores.